This invention relates to a radio paging method and to a base station and a pager receiver both of which are available to the radio paging method.
In general, a radio paging method of the type described is for use in a radio paging system comprising a plurality of subscriber substations, a base station connected through wires to the subscriber substations, and a plurality of pager receivers selected through radio channels by the base station. Unidirectional communication is carried out by such a radio paging method from each of the subscriber substations to the pager receivers through the base station to selectively call up one of the pager receivers. In addition to transmission of a call number signal, message information can also be transmitted from the base station to the pager receivers. Development of semiconductor integration techniques has enabled transmission of such message information to the pager receivers because each of the pager receivers is thereby enabled to carry out complicated processing to receive the message information. In such unidirectional communication, it is preferred to raise a calling rate in each radio channel and to accommodate as many pager receivers as possible in the radio paging system.
A conventional radio paging method is used to transmit, as the message information, only numerals specified by a maximum of ten digits. Each numeral is transmitted following the call number signal. However, a recent requirement is that various kinds of message be sent to the pager receivers as the message information in addition to the numerals. The conventional radio paging method can not satisfy the recent requirement.
Another conventional method can transmit, as the message information, a long message composed of a maximum of 960 characters. This method is disadvantageous in that the calling rate is inevitably reduced in each radio channel because each radio channel is occupied for a long time. Moreover, each subscriber's substation should be provided with an expensive and nonportable input device to produce such a long message. Stated otherwise, the message information can not be always produced everywhere and every time as long as such an input device is not prepared at the subscriber's substation.
It will readily be understood from the above that an increase in the transmission rate would be desirable because a higher performance is thereby given to the radio paging system. However, reception sensitivity is degraded at each pager receiver when the transmission rate increases greatly. Thus, it is desirable that the reception sensitivity is rendered high at each pager receiver and a wide variety of message information can be transmitted from the base station.